Mod Spec® Service

quantitation of histone PTMs using mass spectrometry

Mod Spec Service

Mod Spec® is a mass spectrometry method that is used to measure the relative abundance of > 60 different histone modifications. Mod Spec® is a great starting point to determine if epigenetic changes are occurring in response to disease or treatment. The large number of modifications monitored allows researchers to not only observe expected changes, but to discover unexpected changes, which can be even more informative.

Analyze histone modification changes in:

  • Response to epigenetic inhibitors
  • Normal vs diseased cells
  • Knock-out cells or animals
  • Inhibitor treated xenografts
  • Human biopsies

What our customers are saying about us...

"While working on the molecular mechanism of an epigenetic drug, we outsourced Mod Spec® to Active Motif in order to get a broader overview of the drug-induced changes of histone modifications. Overall, we were very pleased with the quality of the service, the kept timeline and last but not least, the fair price. We found surprising things that were not on our radar before."

Matthias Lauth, PhD
Phillips University
Marburg, Germany
View complete list of testimonials >

The Process

Submit cell pellets or tissue and Active Motif will perform histone extractions, sample preparation, and mass spectrometry using the Thermo Scientific™ TSQ Quantum Ultra™ Triple-Stage Quadrupole Mass Spectrometer. All samples are run in triplicate and data are presented in an easy to understand format. Data delivery typically occurs within 4 - 6 weeks of sample submission.

Sample Requirements

  • Cells required: 2 - 5 million
  • Tissue requirements: 25 - 100 mg

Request a Mod Spec® Services Quote

Histone modifications detected by Mod Spec®
H1.4: K25UN H1.4: K25AC H1.4: K25ME1
H1.4: K25ME2 H1.4: K25ME3 ^H2A: K5UN
^H2A: K5AC ^H2A: K9UN ^H2A: K9AC
^H2A: K36UN ^H2A: K36AC ^H2A1: K13UN
^H2A1: K13AC ^H2A1: K15UN ^H2A1: K15AC
^H2A1: K15UB ^H2A3: K13UN ^H2A3: K13AC
^H2A3: K15UN ^H2A3: K15AC ^H2A3: K15UB
*H3R2UN: K4UN *H3R2UN: K4AC *H3R2UN: K4ME1
*H3R2UN: K4ME2 *H3R2UN: K4ME3 H3R2UN: Q5UN
H3R2UN: Q5ME1 H3: K9UN H3: K9AC
H3: K9ME1 H3: K9ME2 H3: K9ME3
H3: K14UN H3: K14AC H3: K18UN
H3: K18AC H3: K18ME1 H3: Q19UN
H3: Q19ME1 H3: K23UN H3: K23AC
H3: K23ME1 H3: R42UN H3: R42ME2
H3: R49UN H3: R49ME2 H3: Q55UN
H3: Q55ME1 H3: K56UN H3: K56AC
H3: K56ME1 H3: K64UN H3: K64AC
H3: K79UN H3: K79AC H3: K79ME1
H3: K79ME2 H3: K79ME3 H3: K122UN
H3: K122AC H3.1: K27UN H3.1: K27AC
H3.1: K27ME1 H3.1: K27ME2 H3.1: K27ME3
H3.1: K36UN H3.1: K36AC H3.1: K36ME1
H3.1: K36ME2 H3.1: K36ME3 H3.3: K27UN
H3.3: K27AC H3.3: K27M H3.3: K27ME1
H3.3: K27ME2 H3.3: K27ME3 H3.3: K36UN
H3.3: K36AC H3.3: K36ME1 H3.3: K36ME2
H3.3: K36ME3 H4: K5UN H4: K5AC
H4: K8UN H4: K8AC H4: K12UN
H4: K12AC H4: K16UN H4: K16AC
H4: K20UN H4: K20AC H4: K20ME1
H4: K20ME2 H4: K20ME3  


^ Multiple H2A isoforms may contribute to the signal for modifications on H2A.

* H3R2me2 and H3K4me2/3 are mutually exclusive modifications. H3R2 methylation prevents H3K4 methylation. Therefore, H3K4 modifications  are reported only on the H3R2 unmodified peptide. For more information, see Nature. 2007 Oct 18; 449(7164):933-7.

H3.2 may contribute to signals for modifications labeled H3.1.

Name Cat No. Price  
Mod Spec® 25085 Get Quote
Mod Spec<sup>®</sup> data from control HeLa cells and HeLa cells treated for 7 days with 0.5uM GSK-126

Figure 1: Mod Spec® data from control HeLa cells and HeLa cells treated for 7 days with 0.5uM GSK-126.(Click image to enlarge)

GSK126 is an inhibitor that blocks the methytransferase activity of EZH2, resulting in global decreases in H3K27me2 and H3K27me3. A) A selection of H3 modifications are shown from Active Motif’s Mod Spec® assay that confirm significant decreases in H3K27 methylation with concomitant increases in acetylated and unmodified H3K27 (highlighted in yellow). Changes at H3K36 were also detected (highlighted in red). B) A selection of H4 modifications do not show significant changes in response to GSK126 treatment.


EZH2 inhibition results in decreased H2K27me3 levels

Figure 2: Mod Spec® data from control HEK293 cells and HEK293 cells treated for 6 hours with 5 mM sodium butyrate (NaB).

NaB is a general HDAC inhibitor and treatment is expected to increase histone acetylation levels. A) Mod Spec® data for a selection of acetylated and unmodified histone sites is shown. Acetylation is increased at all sites after treatment. Unmodified peptide is displayed for some sites and shows a concomitant decrease after NaB treatment. B) Methylation at various histone residues is not affected by NaB treatment.


How does Mod Spec® work?

  1. Histones are extracted from samples.
  2. Derivatization of histones using propionic anhydride.
    • Mass spectrometry of proteins requires digestion of the proteins into small peptides before being injected into the mass spectrometer. However, if peptides are too small they can not be separated in the LC step and if too big they are too complex to analyze. The most common method of digestion is with trypsin, an enzyme that cleaves proteins at lysine and arginine residues. This presents a problem when analyzing histones since histone tails are rich in lysine, resulting in digested peptides that are too small. Propionylation, using propionic anhydride, blocks cleavage at lysines while allowing digestion at arginines to occur. The resulting peptides are of the appropriate size for mass spec analysis.
  3. Histones are digested with trypsin.
  4. Samples are analyzed on a Triple-Stage Quadrupole Mass Spectrometer.
    • Peptides of the appropriate molecular weight are selected.
    • Peptides are further fragmented in the collision chamber.
    • Peptides fragments of interest are selected and analyzed by mass spectrometry.
  5. Fragments are analyzed and graphed to show changes between samples.
How does Mod Spec™ work?

Search our database of customer publications that have used our Mod Spec® services.